/*********************************************************************************
This code is provided for internal research and development purposes by Huawei solely,
in accordance with the terms and conditions of the research collaboration agreement of May 7, 2020.
Any further use for commercial purposes is subject to a written agreement.
 *  OKVIS - Open Keyframe-based Visual-Inertial SLAM
 *  Copyright (c) 2015, Autonomous Systems Lab / ETH Zurich
 *  Copyright (c) 2016, ETH Zurich, Wyss Zurich, Zurich Eye
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 * 
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation
 *     and/or other materials provided with the distribution.
 *   * Neither the name of Autonomous Systems Lab / ETH Zurich nor the names of
 *     its contributors may be used to endorse or promote products derived from
 *     this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 *
 *  Created on: May 22, 2015
 *      Author: Andreas Forster (an.forster@gmail.com)
 *    Modified: Stefan Leutenegger (s.leutenegger@imperial.ac.uk)
 *    Modified: Zurich Eye
 *********************************************************************************/

/**
 * @file CeresIterationCallback.hpp
 * @brief Header file for the CeresIterationCallback class.
 *        Used to enforce a time limit on the ceres optimization.
 * @author Andreas Forster
 * @author Stefan Leutenegger
 */

#pragma once

#include <ceres/iteration_callback.h>

namespace ze {
namespace nlls {

/**
 * @brief The CeresIterationCallback class tries to enforce a time limit on the
 *        optimization. It does not guarantee to stay within the time budget as
 *        it assumes the next iteration takes as long as the previous iteration.
 */
class CeresIterationCallback : public ceres::IterationCallback
{
 public:

  /**
   * @brief The constructor.
   * @param[in] time_limit Time budget for the optimization.
   * @param[in] iteration_minimum Minimum iterations the optimization should
   *            perform disregarding the time.
   */
  CeresIterationCallback(double time_limit, int iteration_minimum)
      : time_limit_(time_limit),
        iteration_minimum_(iteration_minimum) {
  }

  virtual ~CeresIterationCallback() = default;

  /// @brief This method is called after every iteration in ceres.
  /// @param[in] summary The iteration summary.
  ceres::CallbackReturnType operator()(
      const ceres::IterationSummary& summary)
  {
    // assume next iteration takes the same time as current iteration
    if (summary.iteration >= iteration_minimum_
        && summary.cumulative_time_in_seconds
            + summary.iteration_time_in_seconds > time_limit_)
    {
      return ceres::SOLVER_TERMINATE_SUCCESSFULLY;
    }
    return ceres::SOLVER_CONTINUE;
  }

  /**
   * @brief setTimeLimit changes time limit of optimization.
   *        If you want to disable the time limit, either set it to a large value,
   *        delete the callback in the ceres options or set the minimum iterations
   *        to the maximum iteration.
   * @param[in] time_limit desired time limit in seconds
   */
  void setTimeLimit(double time_limit) { time_limit_ = time_limit; }

  /**
   * @brief iteration_minimum changes the minimum iterations the optimization
   *        goes through disregarding the time limit
   * @param iterationMinimum
   */
  void setMinimumIterations(int iteration_minimum)
  {
    iteration_minimum_ = iteration_minimum;
  }

 private:
  double time_limit_; ///< The set time limit.
  int iteration_minimum_; ///< The set maximum no. iterations.
};

}  // namespace nlls
}  // namespace ze
